A punching press is provided with an interference area for protecting a work holder, to thereby prevent an interference by a punching head with the work holder. The punching head is programmed to be properly positioned for machining a work, and the relative position of the work on a table with respect to the punching head is controlled by a computerized numerical control machine which moves the table to reach such a relative position. If the punching head attempts to enter the interference area, then punch-pressing is prevented, and an alarm is sounded.
Recently, however, the number of types of compound machining equipment which combine a punching press and a laser machining unit has increased, as such compound machining equipment combines the advantages of both a punching press and laser machining unit; one setup enables a free selection of punching, ribbing, forming or laser-cutting, and then punching, hollowing out or contour cutting a work to the desired shape. In such compound machining equipment, therefore, it is necessary to prevent interference between the punching head and the work holders during a punch-pressing process, or between a laser head and the work holders during a laser machining process.